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Abstract

In optics, chirality is typically associated with circularly polarized light. Here we present a novel way to detect the handedness of chiral materials with linearly polarized light. We performed Second Harmonic Generation (SHG) microscopy on G-shaped planar chiral nanostructures made of gold. The SHG response originates in distinctive hotspots, whose arrangement is dependent of the handedness. These results uncover new directions for studying chirality in artificial materials.

Figures (4)

Schematic diagram of the sample geometry of the G-shaped and of the mirror-G shaped sample structures, in a) and b) respectively. In c) and d), the SHG microscopy images of the G-shaped and of the mirror-G shaped sample structures respectively. The white arrows indicate the direction of the linear polarization. The color coded intensities increase from purple, through green, then yellow to red.

In a), b), c), d), e) and f), the SHG microscopy images of the G-shaped sample structures (Fig. 1a) as a function of the sample position angle, in degrees, on the microscope stage. Orientation a) corresponds to that in Fig. 1a. In g), a SHG microscopy image of the same structures positioned at 0°, with the incoming polarization rotated 90° by means of a half wave plate. The white arrows indicate the direction of the linear polarization. Images a) – f) have the same polarization of the incoming beam. The color coded intensities increase from purple, through green, then yellow to red.

In a), b), c) and d), schematic diagram of the sample geometry of the mirror-G shaped sample structures rotated in steps of 90°. In e), f), g) and h), the corresponding SHG microscopy images. The color coded intensities increase from purple, through green, then yellow to red. The red squares emphasize the pattern reproducing the mirror-G unit cell in Fig. 1. The white arrows indicate the direction of the linear polarization, which is identical for all images shown.

In a) to f) SHG microscopy images of the G-shaped sample structures as function of increasing fundamental wavelength from 770 nm to 820 nm in steps of 10 nm. The color coded intensities increase from purple, through green, then yellow to red. The white arrows indicate the direction of the linear polarization.